Good morning! I have an epub built in Sigil from an html file, CSS file, and several images. The epub has been much edited, so I don't want to go back to the original html and start over again. OTOH I have rewritten my final chapter, using Open Office (the OO document will be used to create a PDF for the printed edition). What is the best way to get that revision into the epub? I can for example paste it into a new html file. And I suppose I can make a new epub of just that chapter. But how do I get the new, Sigil-generated epub text into the existing book? Shall I just delete all the old paragraphs, go to the new epub, copy the substitute paragraphs to clipboard, and paste them into the book?

Having typed that question, it now seems quite reasonable to me. Shall I do it?

Good morning! I have an epub built in Sigil from an html file, CSS file, and several images. The epub has been much edited, so I don't want to go back to the original html and start over again. OTOH I have rewritten my final chapter, using Open Office (the OO document will be used to create a PDF for the printed edition). What is the best way to get that revision into the epub? I can for example paste it into a new html file. And I suppose I can make a new epub of just that chapter. But how do I get the new, Sigil-generated epub text into the existing book? Shall I just delete all the old paragraphs, go to the new epub, copy the substitute paragraphs to clipboard, and paste them into the book?

Having typed that question, it now seems quite reasonable to me. Shall I do it?

Thanks!

If you are wanting to do a sleight-o-hand replacement, I use the tweak-EPUB feature that is included in calibre. I explode the epub, replace the desired file with one of the EXACT same name. then click rebuild. Done
Note. this works with any file inside the EPUB (Note: Changing a pictures size, may need other adjustments)

You can add files (HTML, css, images.. etc) to an existing EPUB from Sigil (File -> Add -> Existing Files). You can save just the new final chapter from OOo as an HTML file and add it to the epub you have. (Don't forget to create a backup copy of the epub, just in case anything goes wrong).

In the end, I just pasted the requsite <p class="normal"> tags into my plain-text file to replace the <p> that was already there, checked to make sure that italics were tagged as <em>, and pasted it into the chapter ahead of the old pages. I checked it in Book View and it was fine, so I then deleted what I had originally written. Looks good.